Collapsible table formed of injection-molded half sections

ABSTRACT

A system for injection molding a half-section of a collapsible table that includes a pair of interhinged half-sections. The system is provided with a mold whose dimensions are appropriate to the half-section to be molded therein, and a driven carrier adjacent one end of the mold having cautilevered therefrom parallel core rods that project into the mold. When the carrier is driven to cause the core rods to occupy an “in” position in which the rods are fully within the mold and extend the full length thereof, molten plastic is then injected into the mold to submerge the rods therein. When the plastic cures and rigidifies, parallel reinforcing beams are then created about the rods which are integrated with the resultant half-section. When the carder is driven to withdraw the rods from the mold which are now in an “out” position, the reinforcing beams are then hollow and the resistance of the half-section to bending forces is enhanced.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to a collapsible table having apair of interhinged half-sections, and more particularly to a system forinjection molding a reinforced half-section for a collapsible table.

[0003] 2. Status of Prior Art

[0004] A dining table intended for use only on special occasions, suchas for banquets, must be stored when not in use. Since a dining tableoccupies a relatively large space, the need to store the table presentsa problem, particularly when there are many tables to be stored and thestorage facilities are limited. A preferred form of banquet table istherefore one that is collapsible to form a compact structure thatoccupies relatively little storage space.

[0005] A typical collapsible table includes a pair of interhingedhalf-sections to each of which is hingedly attached a leg assembly. Tocollapse this table its leg assemblies are first folded in against thehalf-sections of the tabletop, and the half-sections are then foldedtogether to reduce the table to a compact structure requiring littlestorage space. To erect the table at its site of use, the half-sectionsare unfolded to form the tabletop and the leg assemblies are folded outto support this tabletop. A collapsible table in this format isdisclosed in the U.S. Pat. No. 5,357,872 to Wilmore.

[0006] The present invention resides in a collapsible banquet tablehaving beam-reinforced half-sections molded of plastic material. Henceof prior art interest is the U.S. Pat. No. to Pinch et al. 6,058,853(2000) which discloses a collapsible banquet table having plastichalf-sections. These are blow molded and reinforced by rigidifiedsheets.

[0007] Because a banquet table may be subjected to heavy loads in thecourse of its use, a reinforced table of the Pinch type serves a usefulpurpose. However, blow molding is a relatively difficult and costlyprocedure, and the need to include rigidified reinforcing sheets adds tothe cost of producing the half-sections of the Pinch table. Consequentlythe expenses incurred in manufacturing a collapsible table of the Pinchtype are substantial and may militate against their sale and use.

[0008] In blow molding, air or other gas must be blown into a parisoncausing it to expand against a mold to form a hollow object whose sizeand shape is determined by the mold. In injection molding, plasticgranules are heated and homogenized in a cylinder until they aresufficiently fluid to permit their injection under pressure into arelatively cold mold where the molten plastic after filling the mold,solidifies to assume the shape and dimensions of the mold cavity. Withthermoplastics, no chemical changes occur within the plastics; hence theprocess is repeatable.

[0009] The reason why injection molding of table half-sections lendsitself to repeatable mass production thereof is that all that isnecessary to produce each half-section is to feed heated molten plasticfrom the nozzle of a screw-type injector cylinder into the mold andafter the half-section bas solidified to remove it from the mold whichis now ill condition to mold the next half-section.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing, the main object of this invention is toprovide a collapsible table whose half-sections are molded of syntheticplastic material and include reinforcing beams to render the tablecapable of supporting heavy loads which seek to deform the table.

[0011] More particularly, an object of this invention is to provide asystem for injection molding a beam-reinforced half-section for acollapsible table whereby the beams are hollow and are integrated withthe section so as to enhance its resistance to bending forces.

[0012] A salient feature of the invention is that each half sectionincludes reinforcing beams parallel to the longitudinal axis of thetable and a reinforcing beam parallel to its transverse axis, wherebybending forces which seek to bend the table along either thelongitudinal or transverse axis are resisted.

[0013] A significant advantage of an injection molding system inaccordance with the invention is that it makes it possible to massproduce table half-sections at relatively low cost.

[0014] Briefly stated these objects are attained by a system forinjection molding a half-section of a collapsible table that includes apair of interhinged half-sections. The system is provided with a moldwhose dimensions are appropriate to the half-section to be moldedtherein, and a driven carrier adjacent one end of the mold havingcautilevered therefrom parallel core rods that project into the mold.When the carrier is driven to cause the core rods to occupy an “in”position in which the rods are fully within the mold and extend the filllength thereof, molten plastic is then injected into the mold tosubmerge he rods therein.

[0015] When the plastic cures and is rigidified, parallel reinforcingbeams are then created about the rods which are integrated with theresultant half-section. When the carrier is driven to withdraw the rodsfrom the mold which are now in an “out” position, the reinforcing beamsare then hollow and the resistance of the half-section to bending forcesis enhanced.

[0016] These parallel reinforcing beams are parallel to the straightlongitudinal axis of the table top and therefore resist bending forceswhich seek to bend his axis. In order to enhance the resistance of thetable top to bending forces which seeks to bend the table along itstransverse axis, the far end of each half section is molded to define achannel-shaped transverse beam.

[0017] This transverse reinforcing beam is created by inserting into themold adjacent the ends of the longitudinally-extending core rods atransverse bar profiled to define when molt plastic is injected into themold a channel-shaped transverse beam forming the far end of thehalf-section, the beam including an inwardly-directed ledge thatunderlies the bar and prevents its withdrawal from the mold.

[0018] In order to jiggle the bar after the completion of molding sothat it can be withdrawn by swinging it out of and away from thechannel-shaped transverse beam, the bar is mounted on a pair of angledarms which are manipulated by a drive mechanism to jiggle the bar.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] For a better understanding of the invention as well as otherobjects and further features thereof, reference is now made to theannexed drawings wherein:

[0020]FIG. 1 is a perspective view of a collapsible table in accordancewith the invention in its erected state composed of an interhinged pairof half-sections;

[0021]FIG. 2 shows the underside of the tabletop;

[0022]FIG. 3 is a transverse section taken through a half-section; and

[0023]FIG. 4 illustrates a system in accordance with the invention forinjection molding each half-section of the tabletop.

[0024]FIG. 5 is a perspective view of the molded end of the half-sectionwhich defines a channel-shaped transverse reinforcing beam; and

[0025]FIG. 6 illustrates the profiled bar which in the mold acts to formthe transverse beam.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The Collapsible Table: Referring now to FIGS. 1 to 3 shown inthese figures in a collapsible table in accordance with the inventionwhose half-sections are reinforced by hollow beams to render the tablecapable of supporting heavy loads without being deformed hereby as whena banquet table is overloaded with pots and plates containing foods acenterpiece and various other more or less heavy items. The resultantdeformation of the tabletop may cause the load to shift and slide offthe table. Hence an important aspect of a collapsible tabletop inaccordance with the invention is that despite the fact that it is formedof a relatively light weight plastic structure, it is neverthelesscapable of sustaining a heavy load without deformation.

[0027] It is to be understood however, that the invention is not limitedto a banquet table, for a similar but smaller version of the collapsibletable may be used as a worktable or for other purposes; retaining theadvantage that when the table is in its collapsible state, the resultantcompact structure requires little storage space.

[0028] The tabletop of the collapsible table shown in FIG. 1 is composedof a pair of like half-sections 10 and 11 whose adjacent ends areinterhinged by a hinge 12. In the operative state of the table, thehalf-sections are coplanar to create a horizontal table surface. Hingedto the underside of half-section 10 is a leg assembly 13, while hingedto he underside of half-section 11 is a leg assembly 14. In theoperative or erect state, the leg assemblies are unfolded to support thetabletop. In the collapsed state, the legs are folded in against thehalf-sections ad the half-sections are then folded together.

[0029] To reinforce the half-section of the tabletop so that the tablecan support heavy loads, each half-section is provided with an array offour parallel beams 15 to 18 which are integral with the half-section.Each beam, is hollow and has a rectangular cross-section.

[0030] Beams 15 and 18 form the longitudinal borders of the half-sectionwhile the inwardly spaced beams 16 and 17 are intermediate to borderbeams and serve to stiffen the somewhat flexible plastic forming thetabletop.

[0031] A hollow beam offers a higher resistance to flexion than a solidbeam and though it requires less plastic than a solid beam and itprovides greater protection against forces which seek to bend and deformthe tabletop.

[0032] The Injection Molding System: Referring now to FIG. 4, shownschematically therein is a system for injection molding a plastichalf-section of the collapsible table illustrated in FIGS. 1 to 3.

[0033] The system includes a rectangular mold 19 whose cavity dimensionsand shape correspond to those of the half-section to be molded,including rounded corners. Adjacent one end of the mold is a carrier 20driven by hydraulic cylinders 21 or other motorized drive means forreciprocating the carrier so that it performs a forward stroke followedby a reverse stroke. Cantilevered from carrier 20 and projecting intomold 11 are four parallel core rods 15R, 16R, 17R and 18R whose lengthand cross-sectional dimensions correspond to those of the reinforcingbeams 15 to 18 to be integrated into the half-section.

[0034] In the forward stroke of carrier 20, the core rods are placedfilly within the mold and are therefore in their “in” position. In thereverse stroke of carrier 20, the core rods are fully withdrawn from themold and therefore they occupy their “out” position.

[0035] When the rods occupy their “in” position, hot molten plastic froma screw cylinder source 22 is injected into the mold to fill it andsubmerge the core rods 15 to 18. When the plastic in the relatively coldmold cures and rigidifies, it forms the half-section having integraltherewith reinforcing beams 15 to 18. And when the rods are withdrawnfrom the mold and are in their “out” position, then the reinforcingbeams are hollow and enhance the resistance of the half-section toflexion forces which seek to deform it.

[0036] Hence, the system makes possible rapid mass production ofhalf-section for when the production of a half-section is completed andtaken out of the mold, all that need be done to repeat the operation isto cause the core rods to re-enter the mold to assume the “in” positionand to then inject molten plastic into the mold to quickly fill it andsubmerge the rods. Finally, after the plastic has rigidified, the corerods are retracted and the half-section is removed from the mold.

[0037] Molding of Transverse Reinforcing Beam

[0038] A collapsible table in accordance with the invention is providedwith a pa of interhinged half-sections 10 and 11 as shown in FIGS. 1 and2. These half-sections are injection molded in a mold, as shown in FIG.4, into which the four longitudinally-extending core rods 15R and 18Rare inserted to define the hollow side beams and the two hollowintermediate beams, all of which are parallel to the longitudinal axisof the table top. These beams therefore act to resist forces which seekto bend the longitudinal axis. When the molten plastic injected into themold hardens about the core rods, the rods are thenhydraulically-retracted so that the molded half-section can be liftedout of the mold.

[0039] In order to enhance the resistance of the table to bending forceswhich seek to bend it along the transverse axis, the far end of eachhalf-section is molded, as shown in FIG. 5, in connection withhalf-section 10 to define a transverse channel-shaped reinforcing beam23 having an inwardly-directed lower ledge 24. This transverse beam atthe end of each half-section of the table top is resistant to forceswhich seek to bend it along its transverse axis.

[0040] In order to form the channel shaped transverse reinforcing beamin each half section of the table top, there is inserted in the moldadjacent its far end a transverse core bar 25 as shown in FIG. 6. Bar 25has a trapezoidal cross section having a flat base 26 and a nose 27projecting from the base. Nose 27 is profiled to define the transverseend beam 23 of the table top half-section.

[0041] It will be seen in FIG. 6 that the inwardly-directed ledge 27 ofthe transverse beam underlies the nose 27 of bar 25. Hence uponcompletion of the molding operation, one cannot simply lift out themolded half-section from the mold in that the ledge of its transversebeam underlies the nose of the core bar.

[0042] In order to free the molded piece from bar 25 so that the piececan be lifted out of the mold, it is then first necessary to, swing bar25 out and away from the molded end channel. Hence bar 25, to accomplishthis movement must be jiggled.

[0043] In order to jiggle bar 25, it is mounted on a pair of parallelarms 28 and 29 which are angled with respect to the vertical axis X.Arms 28 and 29 are driven by a reciprocating drive mechanism.

[0044] The arrangement is such that in the forward stroke of the drivemechanism, arms 28 and 29 which support core bar 25 are raised to swingthe bar sideways out of the channel of the transverse beam. In thedownstroke, the arms take the bar away from the channel so that themolded half-section is now free to be lifted out of the mold.

[0045] Because the table top is provided along its full length withlongitudinally-extending reinforcing beams and at either end with atransverse reinforcing beam, the table top is resistant to whateverbending forces are imposed thereon regardless of their orientation. As aconsequence, tis relatively light weight injection molded plastic tableis capable of sustaining heavy loads which on some occasions it may becalled upon to do.

[0046] While there has been shown preferred embodiments of a collapsibletable in accordance with the invention and a system for mass-producingthe half-sections, it is to be understood that many changes may be madetherein without departing from the spirit of the invention.

1. A system for injection molding a half-section of a collapsible tablehaving a pair of interhinged half-sections supported on leg assemblies,tie half-section, being reinforced by hollow parallel beams integraltherewith, said system comprising: A. a rectangular mold having a cavitytherein whose dimensions and shape are appropriate to the half-sectionto be molded; B. a driveable carrier adjacent an end of the mold havingparallel core rods cantilevered therefrom which project into the mold,said core rods having positions corresponding to the parallel beams ofthe half-section, and having substantially the same length andcross-section; C. drive means to reciprocate the carrier so that in aforward stroke the rods occupy an “in” position filly within the mold,and in a reverse stoke are in an “out” position retraced from the mold;and D. means to inject molten plastic into the mold when the core rodsare in their “in” position to fill the mold and submerges the rodswhereby when the plastic curves and rigidifies, there is then producedthe beam-reinforced half-section, and when the rods are in their “out”position and the half-section is taken out of the mold its beams arethen hollow whereby the resistance of the half-section to flexion forcesis enhanced.
 2. A system as set forth in claim 1, in which the parallelbeams include a pair of border beams extending longitudinally alongopposite sides of the half-section, at least one beam being intermediatethe border beams.
 3. A system as set forth in claim 2, in which betweenthe border beams at spaced positions are a pair of intermediate beam. 4.A system as set forth in claim 1, in which the drive means isconstituted by a motorized mechanism.
 5. A system as set forth in claim1, in which the drive means is constituted by hydraulic cylinders.
 6. Asystem as set forth in claim 1, in which the cavity in the mold isprovided with rounded corners at an end thereof to create correspondingcorners in the half-section.
 7. A system as set forth in claim 1, inwhich the means to inject molded plastic into the mold includes acylinder having an extruder screw in which pellets of thermoplasticmaterial are melted and are exuded from a nozzle.
 8. A collapsible tableincluding a pair of interhinged half-sections, each half-section beingmade by the method set forth in claim
 1. 9. A collapsible table as setforth in claim 8, in which attached to each half-section and hingedthereto is a leg assembly which when the table is collapsed is foldedagainst the table section.
 10. A collapsible table as set forth in claim9, in which each half-section is molded of polyethylene.
 11. A system asset forth in claim 1, in which the half-section of the collapsible tableis further reinforced by a hollow transverse beam having a channel shapeformed at an end of the half-section to resist bending forces which seekto bend the half-section along a transverse axis.
 12. A system as inclaim 11, in which the transverse beam is formed by a transverse bardisposed in the mold having a projecting nose that is profiled to definesaid channel-shaped beam.
 13. A system as set forth in claim 12, inwhich the channel-shaped beam includes an inwardly-directed ledge thatunderlies the nose and prevents tile withdrawal of the moldedhalf-section from the mold.
 14. A system as set forth in claim 13,further including means to withdraw the nose of the bar out of and awayfrom tile channel of the transverse beam upon completion of its moldingso that the half-section can then be lifted out of the mold.
 15. Asystem as set forth in claim 14, in which is provided a jiggle mechanismto swing the bar out of and away from the channel.